In a broadcasting apparatus of background art which records and plays digital video, processing devices such as a device for storing video data and a device for playing video data are controlled using a synchronization signal (see Japanese Patent Application Publication No. Hei 8-140050).
In the broadcasting apparatus of the background art, timings such as process start timings of a memory unit and a playback unit which perform data processing in synchronization with the synchronization signal are designed with consideration given to maximum delays. The maximum delays refer to maximum times needed for processing by units such as the memory unit and the playback unit.
Since processing time needed by each unit differs depending on the bit rate of video data inputted to the digital video recording/playback apparatus, the maximum delay is determined in accordance with the bit rate of the video data. It should be noted that the determination of the maximum delay takes into consideration not only the processing time according to the bit rate of video data, but also deviations in timings of command transfer between the units which depend on the load on each unit, and other unexpected situations. The maximum delay is defined in units of the period of the synchronization signal, which is a signal having a period equal to a frame period.
Moreover, since each unit performs processing in synchronization with the synchronization signal, timings between the units are controlled. In other words, when each unit receives an instruction (e.g., data transfer request) to perform processing in a certain frame, the timing with which the unit that has received the instruction starts the processing is at a frame subsequent to the frame at which the instruction has been received. Moreover, a unit which performs processing subsequent to the foregoing processing performs the processing at a frame later than a frame at which the previous unit has completed the processing.
As described above, the maximum delay is determined in accordance with the bit rate of inputted video data, timings between the units are designed based on the determined maximum delay. Moreover, operation timings between the units are controlled in synchronization with the synchronization signal.
However, since the operation of each unit is synchronized with the synchronization signal, the design of timings between the units becomes complicated. Moreover, in the case where there is a change in the bit rate of inputted video data, operation timings between the units need to be redesigned. However, it is difficult to cope with a bit rate change.